Drive control apparatus for oil pump

ABSTRACT

The present invention provides a drive control apparatus for driving an electric oil pump by supplying it with a predetermined operating voltage so as to decrease a load on the electric oil pump. The drive control apparatus detects a clutch hydraulic pressure supplied to the hydraulic control apparatus for the automatic transmission and drives the electric oil pump so that a required hydraulic pressure is maintained. In this case, the drive control apparatus detects an oil temperature of the hydraulic control apparatus for the automatic transmission, controls the operating voltage of the electric oil pump based on the oil temperature, and supplies the operating voltage to th electric oil pump. Accordingly, the hydraulic pressure supplied from the electric oil pump maintains the hydraulic pressure required for the hydraulic control of the automatic transmission and prevents supply of a greater hydraulic pressure than is required.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an apparatus for controllingthat supply of hydraulic pressure to a hydraulic controller of anautomatic transmission in a vehicle, such as an automobile. Further, thepresent invention is especially suitable for a hybrid vehicle, and avehicle performing an idling stop, or the like. More particularly, thepresent invention relates to an apparatus which controls operatingvoltage of an electric oil pump which supplies a hydraulic pressure to ahydraulic controller of the automatic transmission, based on oiltemperature, when the drive power source of the vehicle is stopped(off).

[0003] 2. Description of Related Art

[0004] Some vehicles such as hybrid vehicles and vehicles which come toan idling stop, automatically stop (turn off) their drive power source(such as an engine and a motor) when the vehicle is stopped (or whenpredetermined conditions are established) in order to reduce exhaustemissions and improve fuel economy. In these vehicles, a mechanical oilpump for supplying a hydraulic pressure to the hydraulic controller ofthe automatic transmission, or an automatic transmission mechanism orthe like, is mechanically interlocked with the drive power source, andtherefore it is stopped when the drive power source is inoperative. Whenthis happens, the hydraulic pressure decreases below that required forcontrolling clutches to be used for transmitting a drive force.Therefore, when the drive power source is restarted, the clutches areengaged only after the rotational speed of the power source hasincreased to a level where a shock is generated.

[0005] Japanese Patent Application Laid-Open No. 8-14076, for example,discloses a system wherein an electric oil pump is electrically drivenby a battery or the like, independently of the drive power source. Thesystem is designed such that, when the mechanical oil pump is stopped,the electric oil pump, which is independent of the drive power source,is driven so as to supply a hydraulic pressure to a hydrauliccontroller, so that a predetermined hydraulic pressure required forhydraulic control is maintained.

[0006] However, as disclosed in the aforementioned patent application,the electric motor for driving the electric oil pump is always operatedunder a constant voltage. Therefore, a greater hydraulic pressure thanis required is generated at some oil temperatures, because of thecharacteristics of the automatic transmission, change in oil viscositydue to oil temperature or the like. This causes an increase in load onthe electric oil pump and the electric motor, thereby increasing theelectric power consumption of the electric motor and decreasing theamount of charge of the battery, which may lead to a decrease inoperation time of the electric motor. In addition, durability of theelectric oil pump and the electric motor is reduced. Furthermore, theelectric oil pump must be designed to withstand a greater hydraulicpressure than is required as described above.

SUMMARY OF THE INVENTION

[0007] Therefore, it is an object of the present invention to provide acontroller for, based on an oil temperature, supplying a determinedoperating voltage to an electric motor for driving an oil pump, so as tosolve the foregoing problems.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1 is a block diagram showing a drivetrain of a vehicleaccording to the present invention;

[0009]FIG. 2(a) is a skeletal view of an automatic transmissionmechanism according to the present invention and FIG. 2(b) is a table ofoperations thereof;

[0010]FIG. 3 is a partial schematic view of a hydraulic circuit of thehydraulic controller;

[0011]FIG. 4 is a block diagram of a control apparatus according to thepresent invention;

[0012]FIG. 5(a) is a graph showing a relationship between the hydraulicpressure and the oil flow rate based on the oil temperature and FIG.5(b) is a graph showing a relationship between the oil temperature andthe operating voltage of the electric oil pump;

[0013]FIG. 6 is a flow chart of a control routine for drive control ofthe oil pump according to the present invention;

[0014]FIG. 7(a) is a time chart for on/off of a drive power sourcestopping flag versus time;

[0015]FIG. 7(b) is a pressure time chart showing clutch hydraulicpressure versus time; and

[0016]FIG. 7(c) is a voltage time chart showing voltage for the electricoil pump versus time;

[0017]FIG. 8 is a flow chart of a control routine for operation of theoil pump based on the drive power source rotational speed N; and

[0018]FIG. 9(a) is a stop flag time chart showing on/off of a drivingpower source stopping flag versus time;

[0019]FIG. 9(b) is a rotational speed time chart showing drive powersource rotational speed versus time;

[0020]FIG. 9(c) is a pressure time chart showing clutch hydraulicpressure versus time; and

[0021]FIG. 9(d) is a voltage time chart showing voltage across theelectric oil pump versus time.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0022] An embodiment of the present invention will now be explained withreference to the drawings. FIG. 1, a block diagram showing a drivetrainof a vehicle to which the present invention is applied, shows a drivepower source in the form of a combination of an engine 2 and amotor/generator (M/G) 3 which output a driving force to an automatictransmission mechanism 5 through a torque converter (T/C) 4. Theautomatic transmission mechanism 5 shifts the gear ratio by which thedriving force is output to the wheels, etc., responsive to certainvehicle driving conditions. The automatic transmission mechanism 5 isprovided with a plurality of friction engagement elements for a shiftchange, and a hydraulic controller 6 for performing the shift change byhydraulically controlling engagement/release of the friction engagementelements, and for controlling the torque converter 4. Moreover, theautomatic transmission mechanism 5 is provided with a mechanical oilpump 7 and an electric oil pump 8 for supplying hydraulic pressure tothe hydraulic controller 6. The mechanical oil pump 7 is interlockedwith the torque converter 4 so as to be driven by the engine 2 and themotor/generator 3. On the other hand, the electric oil pump 8, which isindependent of the driving force of the engine 2 and the motor/generator3, is driven by a motor which receives electric power from a batterywhich will be described later in detail.

[0023] Next, the automatic transmission mechanism will be explainedreferring to FIGS. 2(a) and 2(b). As shown in FIG. 2 (a), a primaryautomatic transmission mechanism 30, disposed on a first shaft which isaligned with an engine output shaft, has an input shaft 37 to which thedriving force is transmitted from the engine 2 (E/G) and themotor/generator (M/G) 3, through torque converter 4 having a lock-upclutch 36. The first shaft carries, in order, the mechanical oil pump 7and the electric oil pump 8 adjacent to the torque converter 4, a brakesection 34, a planetary gear section 31, and a clutch 35.

[0024] The planetary gear section 31 includes a simple planetary gearunit 32 and a double pinion planetary gear unit 33. The simple planetarygear unit 32 is formed by a sun gear S1, a ring gear R1, and a carrierCR that supports a pinion P1 meshed with these gears, while the doublepinion planetary gear unit 33 is formed by a sun gear S2, a ring gearR2, a carrier CR that supports a pinion P2 meshed with the sun gear S1and a pinion P3 meshed with the ring gear S2 in such a manner that bothpinions are meshed with each other. Further, the sun gear S1 and the sungear S2 are each rotatably supported by hollow shafts that, in turn, arerotatably supported by the input shaft 37. Moreover, the carrier CR isshared by both planetary gear units 32, 33, and the pinion P1 and thepinion P2 meshed with the sun gears S1, S2, respectively, are connectedto each other so as to rotate integrally.

[0025] The brake section 34 includes a one-way clutch F1, a brake B1,and a brake B2. A counter drive gear 39 is splined to the carrier CR.Furthermore, a one-way clutch F2 is disposed within the circumference ofthe ring gear R2, and a brake B3 is interposed between the outercircumference of the ring gear R2 and the case. The clutch section 35 isprovided with a forward clutch C1 disposed around the circumference ofthe ring gear R1, and a direct clutch C2 interposed between an innercircumferential surface of a movable member, not shown, and a flangefixed to an end of the hollow shaft.

[0026] A secondary transmission mechanism 40 is disposed on a secondshaft 43 arranged in parallel with the first shaft, i.e., the inputshaft 37. The first shaft, the second shaft and a third shaft formed bydifferential axles (left and right axles) 45 l, 45 r are triangular whenviewed from the side. And the secondary transmission mechanism 40includes simple planetary gear units 41, 42. The carrier CR3 isintegrally coupled to a ring gear R4, and sun gears S3, S4 areintegrally coupled to each other so as to form a Simpson type geartrain. Furthermore, a ring gear R3 is coupled to a counter-driven gear46 to form an input section, and the carrier CR3 and the ring gear R4are coupled to a deceleration gear 47 that serves as an output section.Furthermore, a UD direct clutch C3 is interposed between a ring gear R3and the integrated sun gears S3, S4, and the sun gear S3 (S4) may bebraked by a brake B4 as necessary, and the carrier CR4 may be braked bya brake B5 as necessary. Consequently, the secondary transmissionmechanism 40 can provide three forward speeds.

[0027] A differential apparatus 50 that forms the third shaft has adifferential case 51, and a gear 52 meshed with the deceleration gear 47is secured to the differential case 51. Furthermore, inside thedifferential case 51, a differential gear 53 and left and right sidegears 55, 56 are meshed with each other and are rotatably supported, andleft and right axles 45 l, 45 r extend from the left and right sidegears. Consequently, rotation of the gear 52 is branched correspondingto a load torque, and transmitted to left and right front wheels throughthe left and right axles 45 l, 45 r.

[0028] Next, operation of the automatic transmission mechanism 5 will beexplained referring to the table of operations shown in FIG. 2(b). In afirst speed (1ST) state, the forward clutch C1, the one-way clutch F2,and the brake B5 are engaged. This causes the primary transmissionmechanism 30 to be in first speed, and the decelerated rotation istransmitted to the ring gear R3 in the secondary transmission mechanism40 through counter gears 39, 46. The secondary transmission mechanism40, in which the carrier CR4 is stopped by the brake B5, is in a firstspeed state, and decelerated rotation of the primary transmissionmechanism 30 is further decelerated by the secondary transmissionmechanism 40, and transmitted to the axles 45 l, 45 r through the gears47, 52 and the differential apparatus 50.

[0029] In a second speed (2ND) state, both the forward clutch C1 and thebrake B-2 are engaged, and there is a smooth shift from the one-wayclutch F2 to the one-way clutch F1. This causes the primary transmissionmechanism 30 to shift to a second speed. Meanwhile, the secondarytransmission mechanism 40 is in the first speed state with the brake B5being engaged. Thus, by the combination of the second speed state of theprimary transmission mechanism 30 and the first speed state of thesecondary transmission mechanism 40, second speed can be obtained in theautomatic transmission mechanism 5 as a whole.

[0030] In third speed (3RD), the state of the primary transmissionmechanism 30, in which the forward clutch C1, the brake B-2, and theone-way clutch F1 are engaged, is similar to the aforementioned secondspeed state. A brake B4 is engaged in the secondary transmissionmechanism 40. Then, the sun gears S3, S4 are secured, and the rotationof the ring gear R3 is output from the carrier CR3 as the second speedrotation. Consequently, by the combination of the second speed state ofthe primary transmission mechanism 5 and the second speed state of thesecondary transmission mechanism 40, third speed can be obtained in theautomatic transmission mechanism 5 as a whole.

[0031] In fourth speed (4^(TH)), the state of the primary transmissionmechanism 30, in which the forward clutch C1, the brake B-2, and theone-way clutch F1 are engaged, is the same as in the aforementionedsecond and third speed states. In the secondary transmission mechanism40, the brake B4 is released and the UD direct clutch C3 is engaged. Inthis state, the ring gear R3 is coupled to the sun gear S3 (S4),creating a direct coupling rotation in which both planetary gear units41, 42 rotate integrally. Consequently, by the combination of the secondspeed state of the primary transmission mechanism 5 and the directconnection (third speed) of the secondary transmission mechanism 40,fourth speed rotation can be obtained in the automatic transmissionmechanism 5 as a whole.

[0032] In fifth speed (5TH), the forward clutch C1 and the direct clutchC2 are engaged, and rotation of the input shaft 37 is transmitted toboth the ring gear R1 and the sun gear S1. This causes the primarytransmission mechanism 30 to become in a directly connected state inwhich the gear unit 31 rotates integrally. Meanwhile, the secondarytransmission mechanism 40 is in a direct rotation state in which the UDdirect clutch C3 is engaged. Consequently, by the combination of thethird speed state (direct connection) of the primary transmissionmechanism 5 and the direct connection (third speed) of the secondarytransmission mechanism 40, fifth speed rotation can be obtained in theautomatic transmission mechanism 5 as a whole.

[0033] In reverse (REV), the direct clutch C2 and the brake B3, as wellas the brake B5 are engaged. In this state, reverse rotation is outputfrom the primary transmission mechanism 30, while the secondarytransmission mechanism 40 is held in the first speed state, with thecarrier CR4 also stopped in the reverse rotational direction by thebrake B5. Consequently, by the combination of the reverse rotation ofthe primary transmission mechanism 5 and the first speed rotation of thesecondary transmission mechanism 40, reverse, decelerated rotation canbe obtained.

[0034] In FIG. 2(b), a triangle mark indicates that the engagementelements are operated during engine braking. That is, in first speed,the brake B3 is engaged to secure the ring gear R2, in place of theone-way clutch F2, while in second speed, third speed, and fourth speed,the brake B1 is engaged to secure the sun gear S2, in place of theone-way clutch F1.

[0035] Next, the hydraulic controller 6 will be explained with referenceto FIG. 3 which is a partial schematic view of a hydraulic circuit ofthe hydraulic controller 6, with only the elements necessary forexplaining the present invention shown. It should be noted that theactual hydraulic circuit is much more complicated and includes moreelements.

[0036] As shown in FIG. 3, a gear or the like (not shown) in themechanical oil pump 7 is driven by the aforementioned engine 2 and themotor/generator 3. Then, the mechanical oil pump 7 discharges oil to theautomatic transmission (hereafter referred to as “ATF”) which it intakesthrough a strainer 67, and supplies it to a primary regulator valve 61,where the pressure is regulated to a line pressure. Next, the linepressure is supplied to a manual shift valve 62 or the like. Theelectric oil pump 8 shown by a dashed line in the drawing is driven by amotor M1. The electric oil pump 8 intakes ATF through the strainer 67,and discharges the ATF as a hydraulic pressure to the primary regulatorvalve 61 and the manual shift valve 62 or the like in a similar manner.That is, hydraulic pressure can be supplied to the primary regulatorvalve 61 and the manual shift valve 62 by one, or both, of themechanical oil pump 7 and the electric oil pump 8. The primary regulatorvalve 61 also communicates with the other valves through a hydrauliccircuit (not shown).

[0037] On the other hand, for example, when a manual shift lever 62 a isshifted to a drive range (D), a manual shift valve 62 is brought intocommunication with a neutral relay valve 63 so as to supply hydraulicpressure thereto. The neutral relay valve 63 is in communication with ahydraulic pressure actuator 66 for the clutch C1 and an accumulator 64for the clutch C1 so as to supply a hydraulic pressure thereto andthereby control engagement of the clutch C1. Further, an oil passage incommunication with the hydraulic pressure actuator 66 for the clutch C1is provided with a hydraulic pressure sensor 14 and an oil temperaturesensor 13, to detect, respectively, clutch hydraulic pressure (hydraulicpressure on the hydraulic control apparatus) P_(C1) and temperature ofthe ATF (oil temperature) for engaging the clutch C1.

[0038] Next, the control apparatus according to the present inventionwill be explained referring to FIG. 4. As shown in FIG. 4, the engine 2and the motor/generator 3 are connected with each other such that themotor/generator 3 can be driven by the engine 2 and, conversely, theengine 2 can be driven by the motor/generator 3. The system is alsoarranged so that the driving force may be that of the engine 2 alone,that of the motor/generator 3 alone, or a combination of both at thesame time. The driving force is then input into the torque converter 4and, from the torque converter 4 into the automatic transmissionmechanism 5, where it undergoes a shift change, and then output towheels, not shown. Moreover, as described above, the mechanical oil pump7 and the electric oil pump 8 are constructed so as to supply ahydraulic pressure to the hydraulic controller 6 provided in theautomatic transmission mechanism 5. The hydraulic controller 6 isprovided with the oil temperature sensor 13 and the hydraulic pressuresensor 14.

[0039] The control apparatus 1 includes a control section 10. Thecontrol section 10, which is connected with the motor/generator 3, theelectric oil pump 8, and the battery 11 in such a manner that input andoutput are freely made therebetween, can detect and control theirindividual operations. The control section 10 is connected with anengine rotational speed sensor 15 for detecting rotational speed of theengine 2, a magnetic pole position detection sensor 12 for detecting therotational speed of the motor/generator 3, the oil temperature sensor13, and the hydraulic pressure sensor 14. Moreover, the control section10 is provided with oil temperature detection means 10 a, electric oilpump drive control means 10 b, and battery voltage detection means 10 c.The oil temperature detection means 10 a detects oil temperature T ofthe hydraulic controller 6 based on the signal from the oil temperaturesensor 13. The electric oil pump drive control means 10 b supplies themotor M1 with an operating voltage V for operating the electric oil pump8 (hereafter referred to as an “operating voltage”) determined based onthe temperature detected by the oil temperature detection means 10 a,and drives or stops the oil pump 8 based on the hydraulic pressuredetected by the hydraulic pressure sensor 14 or a driving power sourcerotational speed N of the driving power source detected by the magneticpole position detection sensor 12 and the engine rotational speed sensor15. Further, the battery voltage detection means 10 c detects voltage ofthe battery 11.

[0040] Next, relationship between the hydraulic pressure and flow rateas well as the relationship between the oil temperature and theoperating voltage of the electric oil pump in the hydraulic controller 6of the automatic transmission will be explained referring to FIG. 5(a)and 5(b). In FIG. 5(a), an arrow B indicates the direction in which theoil temperature is increased, in other words, oil temperature T_(A), oiltemperature T_(B), and oil temperature T_(C) are in order of decreasingtemperature.

[0041] As shown in FIG. 5(a), when the oil temperature is T_(A), T_(B)or T_(C), the hydraulic pressure P supplied to the hydraulic controller6 is substantially proportional to the flow rate Q of the and ATF.However, if the flow rate Q of the ATF remains unchanged the hydraulicpressure P varies according the oil temperature T caused by thecharacteristics of the automatic transmission and the change inviscosity resultant from the temperature change. In other words, inorder to obtain the same hydraulic pressure P, the flow rate Q of theATF must change in accordance with change in the oil temperature T. Asan example, the hydraulic controller 6 requires a hydraulic pressureP_(X) to engage the clutch C1. In order to obtain the hydraulic pressureP_(X), a flow rate Q_(A) needs to be supplied at the oil temperatureT_(A), while the same hydraulic pressure P_(X) can be obtained bysupplying a flow rate Q_(B) at an oil temperature T_(B), or supplying aflow rate Q_(C) at the oil temperature T_(C), respectively.

[0042] The flow rate Q output by the electric oil pump 8 can bedetermined based on the operating voltage V. Therefore, a substantiallyconstant hydraulic pressure P_(X), as required, is obtained by supplyingan operating voltage V_(A) when the flow rate Q_(A) is required, anoperating voltage V_(B) when the flow rate Q_(B) is required, and anoperating voltage V_(C) when the flow rate Q_(C) is required,respectively. Then, as shown in FIG. 5(b), a map M of the relationshipbetween the oil temperature T and the operating voltage V of theelectric oil pump can be obtained. Since the map M is stored in theaforementioned control section 10 beforehand, the operating voltagecontrol means 10 b is able to determine the operating voltage V of theelectric oil pump 8 based on the oil temperature T detected by the oiltemperature detection means 10 a, by referring to the map M.

[0043] Next, operation of the control apparatus 1 according to thepresent invention will be explained referring to FIG. 6. In FIG. 6,“OFF” indicates that the oil pump is controlled such that one (or both)of the engine 2 and the motor/generator 3 is driven, and “ON” indicatesthat it is controlled such that both the engine 2 and themotor/generator 3 are stopped. For example, when a driver turns on anignition switch by means of an ignition key, the control routine isstarted (S100), and will be continued until, for example, the ignitionswitch is turned off.

[0044] First, the control section 10 judges whether or not the drivingpower source stopping flag is ON based on, for example, a throttleopening or the like (S101). For example, in normal driving, where one(or both) of the engine 2 and the motor/generator 3 is driven, thecontrol section 10 judges that the driving power source stopping flag isnot ON. Then it judges whether or not the clutch hydraulic pressureP_(C1) detected by the hydraulic pressure sensor 14 is equal to orgreater than a second predetermined threshold value P_(B) (S105). Wheneither of the engine 2 and the motor/generator 3 is driven, a hydraulicpressure is supplied from the mechanical oil pump 7, and therefore, theclutch hydraulic pressure P_(C1) is equal to or greater than the secondpredetermined threshold value P_(B). Consequently, the routine returns(S107) after the electric oil pump drive control means 10 b has stoppedthe oil pump 8 (S106).

[0045] Meanwhile, since the clutch hydraulic pressure P_(C1) is detectedby the hydraulic pressure sensor 14 in this embodiment, the hydraulicpressure supplied to the clutch C1 to be engaged, for example, at thestart of driving, is able to be correctly detected. This enables thehydraulic pressure P_(X) required for engaging the clutch C1, especiallyat the start of driving, to be maintained. Moreover, the clutchhydraulic pressure P_(C1) is detectable irrespective of a change in oiltemperature or the like.

[0046] If the oil pump is controlled such that both the engine 2 and themotor/generator 3 are stopped based on, for example, the throttleopening or the like, the control section 10 judges that the drivingpower source stopping flag is ON (S101), and then judges whether or notthe clutch hydraulic pressure P_(C1) is equal to or less than a firstpredetermined threshold value P_(A) (S102). Immediately after that theengine 2 or the motor/generator 3 is controlled to stop, the rotationalspeed of the engine 2 or the motor/generator 3 gradually decreases, andtherefore, the mechanical oil pump 7 is gradually stopped, that is, thehydraulic pressure supplied from the mechanical oil pump 7 graduallydecreases, leaving sufficient hydraulic pressure. Therefore, the clutchhydraulic pressure P_(C1) is equal to or greater than the firstpredetermined threshold value P_(A). Consequently, the routine returns(S107) after the electric oil pump drive control means 10 b has stoppedthe oil pump 8.

[0047] While the aforementioned steps S100, S101, S102, and S107 arerepeated, the clutch hydraulic pressure P_(C1) decreases to a valueequal to or less than the first predetermined threshold value P_(A),which is detected in Step S102. In this case, first, the oil temperaturedetection means 10 a detects the oil temperature T in the hydrauliccontroller 6, and the control section 10 calculates the operatingvoltage V, while referring to the aforementioned map M based on the thusdetected oil temperature T (S103). Next, the electric oil pump drivecontrol means 10 b duty controls the operating voltage V based on thecalculated result and supplies that controlled voltage to the electricoil pump 8 (S104). In other words, the electric oil pump drive controlmeans 10 b drives the electric oil pump 8 and supplies theaforementioned hydraulic controller 6 with a hydraulic pressure based onthe operating voltage V.

[0048] Subsequently, when the engine 2 or the motor/generator 3 isdriven again, the control section 10 judges that the driving powersource stopping flag is not ON (S101), and then judges whether or notthe clutch hydraulic pressure P_(C1) is equal to or greater than thesecond predetermined threshold value P_(B) (S105). The secondpredetermined threshold value P_(B) is set higher than the firstpredetermined threshold value P_(A) (to be explained later in detail),and the clutch hydraulic pressure P_(C1) is maintained at a level lessthan the second predetermined threshold value P_(B). Therefore, theelectric oil pump 8 is maintained in a driven state and the routinereturns (S107). Consequently, even when the vehicle is in a stoppedstate where the driving power source (the engine 2 and/or themotor/generator 3) has been stopped, the electric oil pump 8 generates ahydraulic pressure based on the operating voltage V and the hydraulicpressure is applied to the hydraulic controller 6 of the automatictransmission. The vehicle starts in this state without any trouble,because the automatic transmission, that is, the torque converter 4, theclutch C1, and the like, function normally with the hydraulic pressuregenerated by the electric oil pump 8. In addition, since the engine 2 orthe motor/generator 3 is driven, the mechanical oil pump 7 is alsodriven, and the clutch hydraulic pressure P_(C1) is increasedaccordingly. When the clutch hydraulic pressure P_(C1) becomes equal toor greater than the second predetermined threshold value P_(B) (S105),the electric oil pump drive control means 10 b sets the operatingvoltage to 0 (S106), in other words, stops the electric oil pump 8 andthe routine returns (S107), such that the driving state of the vehiclereturns to the aforementioned normal driving state.

[0049] As shown in FIG. 7(a), when the driving power source stoppingflag is OFF at time to, one (or both) of the engine 2 and themotor/generator 3 is being driven (S101), and therefore, the mechanicaloil pump 7 is being driven. Consequently, as shown in FIG. 7(b), theclutch hydraulic pressure P_(C1) supplied to the hydraulic controlapparatus for the automatic transmission is maintained at asubstantially constant hydraulic pressure P_(Y) which is higher than thesecond predetermined threshold value P_(B) (S105). In this case, asshown in FIG. 7(c), the operating voltage of the electric oil pump 8 is0 (S106), that is, the electric oil pump 8 is stopped.

[0050] When both the engine 2 and the motor/generator 3 are stopped at atime t1, and the driving power source stopping flag is turned ON asshown in FIG. 7(a) (S101), the mechanical oil pump 7 is also stopped.However, as described above, there is a sufficient residual hydraulicpressure supplied from the mechanical oil pump 7. Therefore, the clutchhydraulic pressure P_(C1) is maintained at a value greater than thefirst predetermined threshold value P_(A) (S102). Moreover, the oil pumpis controlled such that the mechanical oil pump 7 and the electric oilpump 8 are controlled to stop and the clutch hydraulic pressure P_(C1)gradually decreases and becomes equal to or less than the firstpredetermined threshold value P_(A) at a time t2 (S102). Subsequently,the electric oil pump drive control means 10 b refers to the map M asshown in FIG. 5(b) and, based on the oil temperature T detected by theoil temperature detection means 10 a (S103), supplies the electric oilpump 8 with the operating voltage V which is duty controlled as shown inFIG. 7(c) so as to drive the electric oil pump 8 (S104).

[0051] In some cases, while the operating voltage V is supplied to theelectric oil pump 8, the voltage of the battery 11 may vary due to, forexample, a change of the amount of charge. In this case, the batteryvoltage detection means 10 c detects the voltage of the battery 11 andthe electric oil pump control means duty controls the voltage of thebattery 11 so that the voltage of the battery 11 becomes a voltage (forexample, V_(A), V_(B), V_(C)) based on the aforementioned map M. Inother words, the voltage of the battery 11 is controlled to be a stableoperating voltage V so that the hydraulic pressure supplied from theelectric oil pump 8 is maintained at the required hydraulic pressureP_(X) Consequently, the stable hydraulic pressure P_(X) required for thehydraulic controller can be maintained irrespective of the voltage ofthe battery 11.

[0052] If the oil temperature is the oil temperature T_(C), which islow, for example when the engine 2 is stopped immediately after it hasbeen started, the electric oil pump operating voltage V_(C) as shown bya solid line in FIG. 7(c) is supplied by the aforementioned controlroutine (S103, S104). On the other hand, if the oil temperatureincreases, for example, by heat of the engine 2 or the like, to the oiltemperature T_(B) or T_(A), the electric oil pump operating voltageV_(B) or V_(A) shown by a dashed line in FIG. 7(c) is supplied. That is,the clutch hydraulic pressure P_(C1) supplies the hydraulic pressureP_(X) required for the hydraulic control (for engaging the clutch C1)irrespective of a change of the oil temperature T and, at the same time,it also prevents generation of a greater hydraulic pressure than isrequired, enabling the load on the electric oil pump 8 to be decreased.This decreases the electric power consumption of the electric motor M1of the electric oil pump 8, and prevents a decrease in the amount ofcharge of the battery, thereby increasing the operation time. At thesame time, it improves the durability of the electric oil pump 8 and theelectric motor M1. Furthermore, since the load on the electric oil pump8 is decreased, the electric oil pump 8 can be made more compact.Moreover, for example, in a hybrid vehicle, since the electric powerconsumption is decreased as described above, the drive time of themotor/generator 3 is increased, which improves fuel economy and reducesexhaust emissions.

[0053] Subsequently, as shown in FIG. 7(b), the residual hydraulicpressure supplied from the mechanical oil pump 7 runs out such that theclutch hydraulic pressure P_(C1) consists of only the hydraulic pressuresupplied from the electric oil pump 8. Thus, the clutch hydraulicpressure P_(C1) is maintained at the substantially constant hydraulicpressure P_(X) required for the hydraulic control of the automatictransmission. When the electric oil pump 8 is driven with a highresidual hydraulic pressure supplied from the mechanical oil pump 7, aload is generated on the electric oil pump 8. Alternatively, when theelectric oil pump 8 is driven after it has run out of the residualhydraulic pressure supplied from the mechanical oil pump 7, the clutchhydraulic pressure P_(C1) becomes lower than the hydraulic pressureP_(X) required for the hydraulic control. In this case, the firstpredetermined threshold value P_(A) for starting supply of the operatingvoltage V to the electric oil pump 8 is set at a certain pressure atwhich the residual hydraulic pressure supplied from the mechanical oilpump 7 has decreased sufficiently and the clutch hydraulic pressureP_(C1) can maintain the hydraulic pressure P_(X).

[0054] When the hydraulic pressure is supplied from the electric oilpump 8, the clutch hydraulic pressure P_(C1) temporarily increases andis combined with the residual hydraulic pressure supplied from themechanical oil pump 7. However, since the second predetermined thresholdvalue P_(B) is set at a certain value higher than the firstpredetermined threshold value P_(A) so that, even in this case, thehighest value A of the clutch hydraulic pressure P_(C1), for example,does not exceed the second predetermined threshold value P_(B),preventing the electric oil pump 8 from accidentally being stopped anddriven again, i.e., so-called hunting. Further, even if the firstpredetermined threshold value P_(A) and the second predeterminedthreshold value P_(B) are set to be the same value, for example, theelectric oil pump 8 is driven based on the first predetermined thresholdvalue P_(A) with the driving power source stopping flag ON, and it isstopped based on the second predetermined threshold value P_(B) with thedriving power source stopping flag OFF. This prevents the electric oilpump 8 from accidentally being stopped when the driving power source isstopped, or from accidentally being driven when the driving power sourceis driven. In other words, this prevents “hunting.”

[0055] At time t3 as shown in FIG. 7(a), when one (or both) of theengine 2 and the motor/generator 3 is driven, the mechanical oil pump 7is also driven and the driving power source stopping flag is turned OFF(S101). In this case, as shown in FIGS. 7(b) and 7(c), although themechanical oil pump 7 is driven by the clutch hydraulic pressure P_(C1),the sharp rise in the hydraulic pressure supplied from the mechanicaloil pump 7 is delayed for a certain period of time due to resistance ofthe hydraulic circuit or the like. During this period of the time, theclutch hydraulic pressure P_(C1) is supplied. That is, the electric oilpump operating voltage V is supplied. In other words, the driving of theelectric oil pump 8 is maintained such that the hydraulic pressure P_(X)is supplied. Although the hydraulic pressure P_(X) increases combinedwith the driving of the electric oil pump 8, the hydraulic pressureP_(X) has not reached the second predetermined threshold value P_(B)(S105), the electric oil pump operating voltage V is continuouslysupplied. Further, the hydraulic pressure supplied from the mechanicaloil pump 7 sharply rises after a delay of a certain period of time. Whenthe clutch hydraulic pressure P_(C1) becomes equal to or greater thanthe second predetermined threshold value P_(B) at time t4 (S105), theelectric oil pump operating voltage V is set to 0 and the electric oilpump 8 is stopped (S106). After that, the hydraulic pressure is suppliedfrom the mechanical oil pump 7, that is, the vehicle moves into a normaldriving state.

[0056] Meanwhile, when the driving of the electric oil pump 8 is stoppedat the same time the driving power source is driven, for example, thehydraulic pressure P_(C1) may become lower than the hydraulic pressureP_(X) required for the hydraulic control of the automatic transmission.In this case, the second predetermined threshold value P_(B) is set at avalue where the electric oil pump 8 is stopped when the hydraulicpressure from the mechanical oil pump 7 increases to a value which ishigh enough to maintain the required hydraulic pressure P_(X).

[0057] In the aforementioned embodiment, the hydraulic pressuregenerated by the mechanical oil pump 7 is supplied to the hydrauliccontroller 6, and therefore, the driving power source is stopped. Whenthe electric oil pump 8 needs to be driven, the determined operatingvoltage V may be supplied to the electric oil pump 8, thereby decreasingthe load on the electric oil pump 8.

[0058] In the aforementioned embodiment, a vehicle equipped with amechanical oil pump interlocked with the driving power source wasexplained. However, the vehicle does not necessarily have to be equippedwith the mechanical oil pump. Further, any control apparatus is possibleas long as an operating voltage is supplied to an electric oil pumpbased on an oil temperature so as to maintain a required hydraulicpressure.

[0059] Next, an embodiment which is a modification of the aforementionedembodiment will be explained referring to the drawings. In the followingembodiment, the explanation of features which are similar to features inthe aforementioned embodiment will be omitted.

[0060] As described above, the mechanical oil pump 7 is driveninterlocked with the engine 2 and the motor/generator 3, via the torqueconverter 4. Therefore, even if, for example, the hydraulic controller 6of the automatic transmission is not, or be cannot be, provided with thehydraulic pressure sensor 14, the rotational speed of the engine 2 or ofthe motor/generator 3 (hereafter referred to as the “driving powersource rotational speed”) N corresponding to the first and secondpredetermined threshold values in the first embodiment as above, can beobtained from the relationship between the driving power sourcerotational speed N and the clutch hydraulic pressure P_(C1) suppliedfrom the mechanical oil pump 7 and the electric oil pump 8, with the oiltemperature taken into consideration. Further, the electric oil pumpdrive control means 10 b can control the electric oil pump 8 so as todrive or stop it based on the driving power source rotational speed N.

[0061] Hereafter, control of the drive control apparatus for the oilpump based on the driving power source rotational speed N will beexplained referring to FIG. 8 and FIGS. 9(a)-9(d).

[0062] First, when the control routine is started (S200), the controlsection 10 detects the driving power source rotational speed N based onsignals from the magnetic pole position detection sensor 12 and theengine rotational speed sensor 15, and detects the oil temperature T bymeans of the oil temperature sensor 13. As described above, therelationship between the flow rate Q of the ATF and the hydraulicpressure P varies due to a characteristic of the automatic transmissionand due to a change in viscosity with change in the oil temperature orthe like (see FIG. 5(a)). Meanwhile, the flow rate Q of the ATF of themechanical oil pump 7 is determined based on the driving power sourcerotational speed N. Accordingly, the driving power source rotationalspeed N for driving or stopping the electric oil pump 8 can becalculated from the required hydraulic pressure P_(X) and the ATFtemperature, by storing beforehand the relationship between the clutchhydraulic pressure P_(C1), which is based on the oil temperature T, andthe driving power source rotational speed N in the control portion 10.

[0063] As shown in FIG. 9, when the driving power source stopping flagis OFF at time t0, one (or both) of the engine 2 and the motor/generatoris being driven (S201), and the mechanical oil pump 7 is also beingdriven. Then, as shown in FIG. 9(b), the driving power source rotationalspeed N is maintained at a substantially constant rotational speedhigher than the second predetermined threshold rotational speed N_(B)(S205). As shown in FIG. 9(c), the clutch hydraulic pressure P_(C1) ismaintained at a constant hydraulic pressure P_(Y) which is higher thanthe second predetermined threshold value P_(B). Therefore, as shown inFIG. 9(d), the electric oil pump operating voltage V is set to 0, andthe electric oil pump 8 is stopped (S206).

[0064] As shown in FIG. 9(a), when the oil pump is controlled such thatthe engine 2 and the motor/generator 3 are stopped at a time t1, thedriving power source stopping flag is turned ON, and it is judged thatthe driving power source stopping flag is ON (S201). However, as shownin FIGS. 9(b) and 9(c), since the driving power source rotational speedN, which is a rotational speed of the engine 2 or the motor/generator 3,is decreasing gradually, the driving power source rotational speed N isgreater than the first predetermined threshold value N_(A) (S202). Inaddition, the residual hydraulic pressure supplied from the mechanicaloil pump 7 is sufficient, and thus the clutch hydraulic pressure P_(C1)is maintained equal to or greater than the first predetermined thresholdvalue P_(A). Further, the oil pump is controlled such that both theengine 2 and the motor/generator 3 are stopped, whereby the drivingpower source rotational speed N decreases gradually so as to becomeequal to or less than the first predetermined threshold rotational speedN_(A), at a time 2 (S202). Moreover, the clutch hydraulic pressureP_(C1) also decreases gradually and becomes equal to or less than thefirst predetermined threshold value P_(A). The electric oil pump drivecontrol means 10 b refers to the map M (S203), and as shown in FIG.9(d), and the electric oil pump operating voltage V is supplied (S204)so as to drive the electric oil pump 8.

[0065] In addition, when the voltage of the battery 11 varies due to,for example, a change in the amount of charge while the operatingvoltage V is supplied to the electric oil pump 8, the aforementionedbattery voltage detection means 10 c detects the voltage of the battery11, and the voltage of the battery 11 is duty controlled so that itbecomes a voltage (such as, V_(A), V_(B), V_(C)) based on theaforementioned map M. In other words, the voltage of the battery 11 iscontrolled to be a stable operating voltage V so that the hydraulicpressure supplied from the electric oil pump 8 is maintained at therequired hydraulic pressure P_(X). Consequently, the hydraulic pressureP_(X) required for the hydraulic control apparatus can be maintainedirrespective of the voltage of the battery 11.

[0066] As in the case of the aforementioned embodiment, if the oiltemperature is the oil temperature T_(C), which is low, in a case, forexample, where the engine 2 is stopped immediately after it has beenstarted, the electric oil pump operating voltage V_(C) shown by a solidline in FIG. 9(d) is supplied by the control routine (S203, S204) asabove. Meanwhile, when the oil temperature increases, for example byheat of the engine 2 or the like, to the oil temperature T_(B) or T_(A),and the electric oil pump operating voltage V_(B) or V_(A) shown by adashed line in FIG. 9(d) is supplied. That is, while the clutchhydraulic pressure P_(C1) supplies the hydraulic pressure P_(X) requiredfor the hydraulic control (for engaging the clutch C1), irrespective ofa change of the oil temperature T, it also prevents generation of agreater hydraulic pressure than is required, thus enabling the load onthe electric oil pump 8 to be decreased. This decreases the electricpower consumption of the electric motor M1 of the electric oil pump 8,and prevents a decrease of the amount of charge of the battery, therebyincreasing the operation time. At the same time, the durability of theelectric oil pump 8 and the electric motor M1 can be improved.Furthermore, since the load on the electric oil pump 8 decreases, theelectric oil pump 8 can be made more compact. Moreover, for example in ahybrid vehicle, since the electric power consumption is decreased asdescribed above, the drive time of the motor/generator 3 can beincreased, thereby improving fuel economy and reducing exhaustemissions.

[0067] Subsequently, as shown in FIGS. 9(b) and 9(c), when the drivingpower source rotational speed N becomes 0 and the driving power sourceis stopped, the clutch hydraulic pressure P_(C1), consists of only thehydraulic pressure supplied from the electric oil pump 8 because theresidual hydraulic pressure supplied from the mechanical oil pump 7 hasrun out, and is maintained at a substantially constant hydraulicpressure P_(X) required for the hydraulic control of the automatictransmission.

[0068] When the electric oil pump 8 is driven with a high residualhydraulic pressure supplied from the mechanical oil pump 7, a load isgenerated on the electric oil pump 8. Alternatively, when the electricoil pump 8 is driven after it has run out of the residual hydraulicpressure supplied from the mechanical oil pump 7, the clutch hydraulicpressure P_(C1) becomes lower than the hydraulic pressure P_(X) requiredfor the hydraulic control. In this case, the first predeterminedthreshold rotational speed N_(A) for starting supply of the operatingvoltage V to the electric oil pump 8 is set at a certain pressure atwhich the residual hydraulic pressure supplied from the mechanical oilpump 7 has decreased sufficiently and the clutch hydraulic pressureP_(C1) can maintain the hydraulic pressure P_(X).

[0069] When the hydraulic pressure is supplied from the electric oilpump 8, the clutch hydraulic pressure P_(C1) increases temporarilycombined with the residual hydraulic pressure supplied from themechanical oil pump 7. However, even in this case, since the secondpredetermined threshold rotational speed N_(B) is set at a certain valuehigher than the first predetermined threshold rotational speed N_(A), asin the case where the second predetermined threshold value P_(B) is setat a certain value higher than the first predetermined threshold valueP_(A), the highest value A, for example, does not exceed the secondpredetermined threshold value P_(B), preventing the electric oil pump 8from accidentally being stopped and driven again, i.e., preventinghunting. Further, even if the first predetermined threshold rotationalspeed N_(A) and the second predetermined threshold rotational speedN_(B) are set to be the same value, for example, the electric oil pump 8is driven based on the first predetermined threshold rotational speedN_(A) with the driving power source stopping flag being in the ON state,and is stopped based on the second predetermined threshold rotationalspeed N_(B) with the driving power source stopping flag OFF. Thisprevents the electric oil pump 8 from accidentally being stopped whenthe driving power source is stopped, or from accidentally being drivenwhen the driving power source is driven. In other words, this preventshunting.

[0070] At time t3 as shown in FIG. 9(a), when one (or both) of theengine 2 and the motor/generator 3 is driven, the mechanical oil pump 7is also driven and the driving power source stopping flag is turned OFF(S201). In this case, as shown in FIGS. 9(b) and 9(c), the driving powersource rotational speed N increases gradually. The clutch hydraulicpressure P_(C1) increases due to the combination of the driving of themechanical oil pump 7 and the driving of the electric oil pump 8 so asto exceed the hydraulic pressure P_(X). However, the driving powersource rotational speed N is less than the second predeterminedthreshold rotational speed N_(B) (S205) or, in other words, the clutchhydraulic pressure P_(C1) has not reached the second predeterminedthreshold number P_(B). Therefore, the driving of the electric oil pump8 is continued. In this case, as in the aforementioned embodiment, theautomatic transmission functions normally and starts without troubleutilizing the hydraulic pressure from the electric oil pump 8. Further,the hydraulic pressure supplied from the mechanical oil pump 7 sharplyrises after a delay of a certain period of time. When the driving powersource rotational speed N becomes equal to or greater than the secondpredetermined threshold rotational speed N_(B) at a time point t4 (S205)and the clutch hydraulic pressure P_(C1) becomes equal to or greaterthan the second predetermined threshold value P_(B), the electric oilpump drive control means 10 b sets the operating voltage to 0 and stopsthe electric oil pump 8 (S206). Then, the hydraulic pressure is suppliedfrom the mechanical oil pump 7, that is, the vehicle returns to itsnormal driving state.

[0071] When the driving of the electric oil pump 8 is stopped at thesame time the driving power source is stopped, for example, hydraulicpressure P_(C1) may become lower than the clutch hydraulic pressureP_(X) required for the hydraulic control of the automatic transmission.Therefore, the second predetermined threshold rotational speed N_(B) isset at a value where the electric oil pump 8 is stopped when thehydraulic pressure from the mechanical oil pump 7 has increased to avalue sufficient to maintain the required hydraulic pressure P_(X).

[0072] In the aforementioned embodiment, a control apparatus accordingto the present invention is employed in a hybrid vehicle in which thedriving power source is a combination of an engine and amotor/generator. However, the present invention is not limited to theabove embodiment, and may be employed in any drive control apparatus aslong as a hydraulic pressure is supplied from the electric oil pump andthe hydraulic temperature is varied.

[0073] The invention may be embodied in other specific forms withoutdeparting from the spirit or essential characteristics thereof. Thepresent embodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

What is claimed is:
 1. A control apparatus for generating a hydraulicpressure for hydraulic control of an automatic transmission in avehicle, the automatic transmission having a hydraulic controller whichperforms a shift change through engagement/disengagement of a pluralityof friction engagement elements responsive to the hydraulic pressure,said control apparatus comprising: an electric oil pump; oil temperaturedetection means for detecting an oil temperature of oil supplied to thefriction engagement elements of the hydraulic controller, and electricoil pump drive control means for driving the electric oil pump bysupplying the electric oil pump with an operating voltage determinedbased on the oil temperature detected by the oil temperature detectionmeans, so that a hydraulic pressure required for the control of theautomatic transmission is maintained.
 2. A control apparatus for an oilpump according to claim 1, wherein the vehicle has a driving powersource and further comprising: a mechanical oil pump which is driven bythe driving power source and which supplies at least a portion of thehydraulic pressure supplied to the hydraulic controller.
 3. A controlapparatus for an oil pump according to claim 2, further comprising: aspeed detector for detecting rotational speed of the driving powersource; and judgement means for determining a hydraulic pressurerequired to be maintained, based on the detected rotational speed of thedriving power source.
 4. A control apparatus according to claim 1,further comprising: a battery which supplies a current for driving theelectric oil pump, and battery voltage detection means for detecting avoltage of the battery; and wherein the electric oil pump drive controlmeans drives the electric oil pump by supplying the electric oil pumpwith an operating voltage determined based on the voltage detected bythe battery voltage detection means and the oil temperature detected bythe oil temperature detection means so that the hydraulic pressurerequired for the hydraulic control of the automatic transmission ismaintained.
 5. A control apparatus according to claim 1, furthercomprising: a pressure detector for detecting a hydraulic pressuresupplied to the friction engagement elements; and judgement means fordetermining a hydraulic pressure required to be maintained, based on thedetected hydraulic pressure supplied to the friction engagement elementsof the automatic transmission.
 6. A control apparatus for an oil pumpaccording to claim 2, wherein the driving power source comprises anengine and a motor for transmitting a driving force to an input shaft ofthe automatic transmission, and the vehicle is a hybrid vehicle in whichthe engine and the motor are freely driven and stopped in accordancewith a driving state.